Sunday, March 22, 2009

US Climate Update: Driest Start to Year on Record

From StormX:

According to the National Climatic Data Center, the first two months of 2009 ranked as the driest on record in the lower 48 states. Precipitation was especially scarce in the mid-Atlantic region, where Virginia, New Jersey, and Delaware also recorded their driest start to the year on record. Widespread dryness was also experienced in south Florida, Texas, and New Mexico.

At the Storm Exchange science center in State College, PA, a team of Ph.D. meteorologists is carefully monitoring the nationwide lack of rainfall and its implications for agriculture. Unusually cool water in the northern Pacific Ocean, along with a La Nina event in the tropical Pacific, have influenced the weather patterns in recent months and will continue to play a role this spring....Driest Start to Year on Record continues, including the forecast map.

Drought over north America has been correlated to the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation....

*Note: Although the AMO is in it's warm phase, the monthly sea surface temperature anomaly is currently negative. This happens. During the 30-year warm phase of the PDO that ended in September 2007, there were months in which the anomaly fluctuated in the opposite (cooler) direction. The east coast drought appears closer to the historical record for -AMO/-PDO. It should break when the AMO anomaly rises. This stuff is so exceedingly complex that it is probably impossible to model with any degree of resolution (granularity), it is more about shading the odds in one direction or another. If you want certainty, go rig a market (or something).Some of our other posts on the PDO:

...There are several theories as to what caused the demise of the Moche political structure. Some scholars have emphasised the role of environmental change. Studies of ice cores drilled from glaciers in the Andes reveal climatic events between 536 to 594 AD, possibly a super El Niño, that resulted in 30 years of intense rain and flooding followed by 30 years of drought, part of the aftermath of the climate changes of 535–536.[3]These weather events could have disrupted the Moche way of life and shattered their faith in their religion, which had promised stable weather through sacrifices.

The BBC had a show on the Moche a while back. Here's what they say happened:

...If the weather on the coast was the opposite, then it suggested a 30-year El Nino - what climatologists call a mega El Nino – starting at around 560 AD, which was followed by a mega drought lasting another 30 years. Such a huge series of climatic extremes would have been enough to kill off an civilization – even a modern one. Here, at last, was a plausible theory for the disappearance of the Moche. But could it be proved?...

It turns out that the Moche adapted to the 30 years of floods and the 30 years of drought which followed.They ended up killing themselves after surviving all that:

...Dillehay now put together a new theory. The Moche had struggled through the climaticdisasters but had been fatally weakened. The leadership - which at least in part claimed authority on the basis of being able to determine the weather – had lost its authority and control over its people. Moche villages and and/or clan groups turned on each other in a battle for scare resources like food and land. The Moche replaced ritual battles and human sacrifices with civil war. Gradually they fought themselves into the grave....